A sub-class of chromatin released from isolated nuclei by trypsin will be further characterized. Purification by sedimentation through sucrose gradients has been facilitated by including a supernatent extract from trypsin treated chromatin. Preparative quantities of this extract will be used to further define parameters for fractionation and enhance purification. An attempt will also be made to devise an affinity fractionation method using imidazoyl carbamate derivatized HMG protein sepharose columns. HMG 14 and 17, known to bind transcriptionally active chromatin, are candidates for the affinity method. Attempts will be made to lower the trypsin or protease window required for release of this sub-component, below the level actually required for chromatin dispersal. This will require the use of alternative, non-proteolytic spreading reagents. Also continued are studies involving single-stranded configurations of chromatin. To be further characterized is an apparent ability of exonucleolytic enzymes to induce a single-stranded protected state in isolated nucleosomes. Possible conformational changes will be further investigated by a variety of probes to the protein core. DNase I induced single-stranded states will also be investigated, especially with respect to the identity of single-stranded gap regions.